Texas A&M University-Kingsville: AKM Digital Repository
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1689 research outputs found
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Evaluation of Rio Grande River's hydrochemical characteristics and applicability for irrigation
No full textElevated salt levels in water used for irrigation can lead to poor performance and productivity of crops. Detrimental effects of high salt levels in irrigation water include the prevention of plants to absorb nutrients and can affect crop growth. Thus, it is critical to evaluate water quality across time and location to ensure efficient water use and best irrigation water management practices. The Lower Rio Grande Valley (LRGV) in South Texas is heavily dependent upon ditch irrigation with districts being reliant on the Rio Grande River (RGR) to support the production of their staple crops. Irrigation districts utilize an irrigation delivery system to transport water through pipelines, canals, and resacas to deliver water to end users. To date, no detailed studies have been conducted to quantify fluxes in salinity levels and their variations in this region. This research provides temporal and spatial evaluations of the RGR’s hydrochemical characteristics at seven sites within selected irrigation districts in the LRGV. Parameters used in the evaluation include electrical conductivity, pH, temperature, total dissolved solids, and concentrations of major ions such as bicarbonate, calcium, carbonate, chloride, magnesium, nitrate, potassium, sodium, and sulfate. Chemical indices used are salinity hazard, sodium adsorption ratio, sodium percentage, residual sodium carbonate, magnesium hazard, Kelly’s Ratio, and permeability index. The temporal and spatial variations of these indices and the correlations among them were evaluated statistically using ANOVA. The RGR water was also assessed for agricultural purposes using water classification diagrams such as Doneen, Piper’s, Richard’s, and Wilcox diagrams. Through the study, the water was deemed permissible to doubtful for irrigation use and significant changes in the water quality were identified temporally. Results from this research provide comprehensive spatial and temporal information on variations of the RGR water quality along the river and help irrigation districts with planning and management activities
Effects of Citrus tree phenology on color morphology and candidatus liberibacter asiaticus acquisition potential of Diaphorina citri kuwayama (Hemiptera: Liviidae)
No full textThe Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae) is an economically significant pest that vectors the bacterial pathogen Candidatus Liberibacter asiaticus (CLas), associated with Huanglongbing (HLB) disease. Diaphorina citri adults exhibit three abdominal color variants of blue, grey, and yellow, which are linked to traits such as flight ability, insecticide resistance, and CLas acquisition. Color morph composition of field-collected D. citri from commercial citrus groves and residential trees in South Texas were evaluated to determine the seasonality of the three variants and assess their CLas status. D. citri samples were evaluated for their sex ratio, morphometric parameters, CLas status, and presence of endosymbionts. In both settings, the yellow color morph was dominant when young flush shoots are present, while the blue morph was the dominant color between flush cycles. Laboratory studies indicated D. citri color morphs were interchangeable depending on flush stage. On mature shoots, blue D. citri remained blue, but a significant proportion of grey and yellow also turned blue within two weeks. In contrast, on young flush shoots, yellow remained yellow while some blue and grey D. citri morphed into yellow. There was no significant effect on color morph on the percentage of CLas-positive psyllid, but there was a trend of higher bacterial titer in yellow relative to blue morphs. Multivariate analysis indicated that maximum temperature and total rainfall four and six weeks prior to D. citri collection were negatively correlated with the percentage of CLas-positive psyllids. The primary and secondary endosymbionts, Candidatus Carsonella ruddii and Candidatus Profftella armature, were present in all three D. citri color morphs. This study showed that citrus tree phenology regulated the color morph composition of D. citri, which can affect CLas transmission and dynamics in groves as well as the effectiveness of vector management
The coupled effects of exceptional drought and climate change on forest structure, tree diversity, and aboveground biomass in East Texas, USA.
No full textDrought-induced tree mortality has been reported locally and globally. East Texas was hit by Hurricane Rita in 2005 and Hurricane Ike in 2008 and an exceptional drought in 2011. The 2011 drought killed 65.5 million trees in East Texas. While effects of drought on forest demographics have been well studied, long-term drought impacts on stability and resilience haven't been fully explored. My study's goal was to understand the impacts of drought
on forest demographics and to predict coupled effects of drought and climate change on aboveground biomass (AGB). I utilized 20 years of Forest Inventory and Analysis (FIA) data to explore historical trends in tree mortality, biomass loss, and consequent changes in forest
diversity, stability, and resilience. I used repeated measure ANOVA, mixed effect models, and the rFIA package to analyze data. During drought, annual mortality rates (2.29% year-1) and biomass loss (0.58% year-1) increased significantly. Seven of the ten most dominant species in east Texas declined within their range during the drought. The results showed that east Texas
forests are resilient to disturbances but are currently undergoing a recovery phase. I took Angelina National Forest in East Texas to simulate aboveground biomass (AGB) using the LANDIS-II model. Three climate scenarios (Business as usual, BAU), low (RCP2.6), high
climate change (RCP8.5) with and without drought were used to simulate AGB in the next 100 years. The AGB is projected to decline under all six simulation scenarios and highest under RCP2.6 with drought (-20%). The effect of drought and climate change on AGB varies between
species. The species with higher initial AGB density, such as loblolly and shortleaf pine, water oak, and sweetgum are projected to decline. Historical analysis and future modelling confirm that severe drought coupled with a hotter and drier climate had affected east Texas forests and will significantly affect forest structure, diversity, productivity, and stability for the foreseeable
future
Assessing resilience of forests to wildfires and fuel management in northern California through forest inventory and aerial photography analyses
No full textIn California, large-scale tree mortality has occurred due to a combination of increased drought and intensified wildfires. Long-lasting fire suppression, logging, and overgrazing resulted in an increased density of trees and hazardous fuels accumulation. In combination with
climate change, this has led to larger and higher intensity wildfires. I investigated how altered forest structure after optimal management improves forest resilience to wildfires and determined which factors are most important to predicting burn severity. My study area focused on the
Lassen and Plumas National Forests in northern California, especially the area burned by the Chips Fire. I used Forest Inventory and Analysis (FIA) data to examine tree mortality patterns and the Forest Vegetation Simulator (FVS) to simulate how wildfires and management affects
forest resilience. I used National Agriculture Imagery Program (NAIP) imagery to estimate burn severity and used regressions to determine which factors are best at predicting it. The simulation showed that heavily thinning resulted in higher forest resilience. For both California mixed conifer and Jeffrey pine forest types, tree-size-related structural diversity has a negative
relationship with forest resilience because of fuel continuity, but species diversity was not related
to forest resilience. Time since most recent fire, weather, and climate variables were the most important predictors of burn severity. Forest managers can use information from my burn severity models to map burn severity risk and to help determine where to apply fuel treatments.
With climate change predicted to worsen droughts and increase the area burned by fires in the future, it is important for forest managers to make decisions on what the optimal levels of thinning, prescribed burning, and fuel reduction are for managing forests in California, which
should be assisted by the results of my research
Analysis of capital and operating cost drivers in transit systems
No full textThis research analyzes and relationships between the capital and operating costs of the transit agencies before and after the normalization of the costs. The study also discusses the funding priorities of transit agencies across different categories of the performance measure. This study relates the Passengers Per Hour (PPH), transit agency Vehicles Operated in Maximum Service (VOMS) with the operating costs of transit agencies. Transit agencies that receive the federal fund must submit their asset inventory, condition assessments, and performance targets to the National Transit Database (NTD). Based on the performance targets, transit agencies invest in different categories of performance measures. The percentage of funds invested by different agencies on different categories of performance measures is determined and priority investments made by the agencies are calculated and compared with the total fund invested by all transit agencies in this study. The total capital and operating costs invested under different headings by the transit agencies are calculated and comparisons were made before and after the normalization of the total costs by plotting the data. The normalization of the costs is done using the Passengers Per Hour (PPH) of the transit agencies. The total operating costs of the transit agencies are related to the PPH and agency VOMS by plotting the data of the transit agencies
Outdoor education research in Texas 4-H
No full textThe COVID 19 Pandemic Shutdown created a lot of challenges for Texas A&M AgriLife Extension County Extension Agents, with the inability to hold indoor traditional 4-H programs a move outside was made by many programs. The purpose of this study is to determine Texas A&M AgriLife Extension County Extension Agents' level of interest in Outdoor Education/ Wildlife project areas training and workshop development, measure the confidence of agents to provide quality Outdoor Education/ Wildlife project area workshops, and determine what resources (training, Explore Guides, equipment/gear contacts, etc.) agents need or would like developed to be able to offer the Outdoor Education/ Wildlife project area in their counties. Offering these project areas in Concho County 4-H has shown a total enrollment increase of forty-eight percent. While 4-H has always had outdoor education, the potential for more growth is there and opens a door for Extension to reach clientele that has been missed in the past. According to a study done by the University of Florida; Studies show that positives changes are seen in children who go through an Outdoor Education Program
Interpreting soil health metrics in semi-arid grazinglands: an assessment of measurement approaches and relational gradients
No full textThe health of the soil resource has received considerable focus recently largely due to its importance to many ecological processes. Although cropland systems have been considerably studied, questions remain regarding the measurement and relationships among soil health metrics in grazinglands systems. To address some of these questions, nineteen ranch properties were sampled totaling 17,347 ha across Oklahoma and Texas in 2019 to evaluate cost effective soil carbon measurement strategies and soil health relationships across soil textures. Primary takeaways from the effort include a) more effective tools are still needed to reduce the cost of sampling and estimate accuracy of soil organic carbon concentrations in heterogeneous landscapes, b) Soil organic matter has a positive relationship with increasing soil available water holding capacity, however the magnitude is not universal, it is mediated across soil texture classes, and c) strong correlations were identified among rangelands, fine-medium textured soils, reduced bare ground, and robust soil biological biomass. Conversely croplands, and to a lesser extent pasture sites, tended to be more closely associated with coarse textured soils, increased bare ground (on croplands), and decreased biological biomass. Ultimately, total microbial biomass and its constituents along with soil organic matter provided the greatest contribution to the explaining the variation in this data set and were most closely associated with rangelands, suggesting that soil microbial biomass and soil organic matter should be considered in rangeland monitoring activities on semiarid grazinglands in the United States Southern Great Plains
A phenomenological study to understand the impact of COVID-19 on mental health among Generation Z pharmacy students
No full textThe COVID-19 pandemic, an unprecedented global crisis, had posed unique challenges to the mental health of Generation Z (Gen Z) pharmacy students born between 1997-2012. This dissertation examined the profound impact of the pandemic on the mental health of this specific demographic. It shed light on the multifaceted factors at play due to the shift to an altered online learning environment. This study explored the experiences, stressors, coping mechanisms, and consequences of the pandemic's influence on Gen Z pharmacy students' mental health through a comprehensive research approach.
The research draws on qualitative methodologies to investigate the prevalence of mental health issues such as anxiety, depression, and feelings of isolation among pharmacy students within the Gen Z pharmacy cohort. It examined their stressors, including academic pressures, social isolation, financial concerns, and the uncertainty of the pandemic's duration.
Furthermore, this dissertation examined the coping strategies employed by these students to mitigate the mental health challenges posed by the pandemic. It assessed the role of social support systems, access to mental health resources, and the effectiveness of online interventions in promoting mental health.
The findings of this study provided critical insights into the unique vulnerabilities and resilience factors of Gen Z pharmacy students in the face of a global crisis. By understanding the multifaceted nature of COVID-19's impact on their mental health, higher education institutions and policymakers can develop targeted interventions and support systems to promote this vital student population's mental health and academic success. This research underscored the urgency of prioritizing mental health resources and fostering a supportive environment for Gen Z pharmacy students as they navigated the challenges brought about by the COVID-19 pandemic and any future pandemics
Further development and use of Ballistic Testing Apparatus for composite armor
No full textLight-weight composite armor greatly protects our military and law enforcement but needs more developmental testing. This work continues development of a federally funded ballistic testing system started by F. Solis, with a current objective of obtaining 200+ m/s impact velocity and 500+ J of impact energy. Contributors besides Ancira and Peel include grant PI Dr. Shah Alam and undergraduate student helpers. The ballistic testing system is a vacuum cannon assisted by compressed air. The cannon was updated from a PVC pipe with a sabot projectile system using only atmospheric pressure to a steel pipe with a fast-acting, powered ball valve and a high-pressure booster system, all of which can withstand 2100 kPa (300 psi). Going to a steel barrel, using low-friction and light sabots, and adding a compressed air booster, greatly increased the impact velocity of the system’s penetrator. A data acquisition system, using vibration sensors, photoelectric sensors, and pressure transducers was developed. The 2-part sabot that carries a penetrator was upgraded with new designs and materials. With the highest recorded velocity of 165 m/s and energy of 367 J at a boost pressure of 717 kPa (104 psi), the system has not reached the desired velocity or energy but could exceed those if a shorter, larger diameter pipe tank is installed. Blow-by, tank geometry, and slower ball valve opening times are likely reasons for lower than desired velocities. The Ballistic Testing System is still a useful tool for testing ballistic panels
Excavating machines using adjustable linkages
No full textExcavators or backhoes are construction machines that are employed to create foundations, holes or trenches by moving or digging dirt through their attached end buckets. Excavators have been widely used for various construction or other projects. Tracked excavators are suitable for heavy-duty projects or on harsh terrain conditions because of their outstanding traction, excellent stability and high digging depth. Wheeled ones are preferred for inner-city or urban projects due to their dexterous maneuverability in narrow space and low impact to the contact ground. An excavator arm consists of bucket, stick and boom that are connected serially by R joints. The arm is pivoted to the excavator’s house that rotates with respect to its undercarriage. An excavator performs its tasks through its arm motion together with its rotatable house and locomotive undercarriage. The three R joints of an excavator arm have parallel axes and form its arm motion plane. They are driven by their corresponding hydraulic cylinders. The moving trajectories and orientations of the bucket of an excavator for digging or other tasks are generated from the three driving cylinder linkages of its arm. The reachable workspace of the bucket on its arm motion plane depend on the dimensions of the three arm linkages. The workspace has no flexibility if the dimensions of the three arm linkages of an excavator are fixed, which limits the applications of the excavator. In order for an excavating machine to have workspace flexibility, one or more motion related parameters of its three arm linkages have to be adjustable. This research aims at improving operation flexibility of excavators through using adjustable arm linkages. Excavators without and with adjustable parameters are analyzed and simulated. Their performances are evaluated and compared. The results from this research will provide some useful guidelines for developing excavating machines